static void Main(string[] args)
{
ChildClass t1 = new ChildClass();
t1.SomeVirtualMethod("");
((ParentClass)t1).SomeVirtualMethod("test");
t1.SomeFinalMethod("");
((ParentClass)t1).SomeFinalMethod("test");
ParentClass t2 = new ChildClass();
t2.SomeVirtualMethod("");
((ChildClass)t1).SomeVirtualMethod("test");
t2.SomeFinalMethod("");
((ChildClass)t1).SomeFinalMethod("test");
Console.ReadKey();
}